This disclosure relates to a seal shaft incorporated into an air cycle machine that supplies air to an aircraft cabin.
Known air cycle machines include a turbine rotor driven to rotate a shaft and in turn drive a compressor rotor. The air cycle machine houses the turbine rotor in a turbine section and houses the compressor rotor in the compressor section. Typically, bearings are incorporated into a housing to support the shaft for rotation. One known type of compressor bearing is an air bearing. Seal shafts are often used in air cycle machines, particularly the air cycle machines that utilize air bearings. The seal shafts control the flow of air near rotating interfaces within the air cycle machine.
One type of shaft seal includes radially extending holes that facilitate exhausting surplus air from the air cycle machine. During operation, the compressor section, the turbine section, or both, may generate the surplus air. If the surplus air is not exhausted, the surplus air tends to move between the compressor section and the turbine section, which can make the air cycle machine less efficient. Under some conditions, surplus air still moves between the compressor section and the turbine section, even with the holes. In the past, the shaft seal did not adequately control the flow surplus air flow between the compressor section and the turbine section.